Waec Physics 1992 Past Questions and Answers

Question 61:

• WAEC 1992

(a) Explain what is meant by the following statement. The specific latent heat of fusion of ice is \(3.4 \times 10^{5}Jkg^{-1}\).
(b) Describe an experiment to determine the specific latent heat of fusion of ice. State two precautions necessary to obtain an accurate result.
(c) Using the kinetic theory of matter, explain why ice can change to water at 0°C without any change in temperature.

Question 62:

• WAEC 1992

(a)(i) What is meant by resonance?
(ii) Outline the necessary steps taken in a simple experiment to illustrate top resonance
(iii) Explain why a vibrating tuning fork sounds louder when its stem is pressed against a table top than when held in air.
(b) Explain with the aid of diagrams, how a concave mirror could be used to: (i) Ignite a piece of carbon paper; (ii) produce an exact copy of a picture on a screen.

Question 63:

• WAEC 1992

(a) Draw a simple labelled diagram illustrating the principle of a step-down transformer and explain how it works
(b) State three ways by which energy is lost in a transformer and how they can be minimized.
(c) If a transformer is used to light a lamp rated at 60W, 220V from a 4400V a.c. supply, calculate the; (i) ratio of the number of turns of the primary coil to the secondary coil in the transformer (ii) current taken from the main circuit if the efficiency of the transforme is 95%.